Investigating the potential of bornean plant as natural turbidity removers and enhancers of Mahakam River water quality

The Mahakam River, coursing through East Kalimantan, Indonesia, is suffering from significant water quality problems. These issues stem from a combination of factors: the heavy use of coal barges, industrial operations, and the runoff that comes from both agriculture and everyday life. The people of Loa Kulu and Loa Janan, two nearby villages, rely on this river for their fresh water needs, particularly for aquaculture. This study aims to evaluate the effectiveness of Kalimantan plant powders, Solanum ferox, Sauropus androgynus, Moringa oleifera, and Carica papaya in turbidity removal as well as to test S. ferox extract as a natural coagulant candidate to improve the water quality of the Mahakam River. A three-phase experimental design was employed. In the first phase, powders of four plant species were tested for coagulation activity in vitro using kaolin-simulated turbid water (200, 500, and 1000 NTU) via standard jar test procedures at doses of 0.05, 0.10, and 0.15 g/L each powder plant. In the second phase, the best-performing plant (S. ferox) was further processed into an ethanolic extract (400 ppm) and tested at doses of 1, 2, and 3 mL/L against the same turbidity levels in vitro. In the third phase, the optimal S. ferox extract dose was applied to Mahakam River water samples, to assess its effect on multiple water quality parameters. All four plant powders demonstrated substantial coagulation efficacy, with Percentage Coagulation Activity values ranging from 91.95 to 98.18% across all tested turbidity levels. S. ferox powder exhibited the highest efficacy at 200 NTU, while M. oleifera performed best at 500 and 1000 NTU. When applied as an extract to actual Mahakam River water at an optimal dose of 2 mL/L, S. ferox extract significantly reduced turbidity by 60.10%, TDS by 42.86%, Fe concentration by 24.15%, and E. coli by 92.31%. While TSS temporarily increased consistent with successful floc formation during the coagulation-flocculation process, the overall improvement in water clarity and chemical safety was evident. Significance: These findings demonstrate that locally available Bornean plant extracts, particularly S. ferox, offer a viable, eco-friendly alternative to synthetic chemical coagulants for water treatment in the Mahakam River basin. This study represents the first comprehensive investigation of Bornean plant extracts for holistic Mahakam River water remediation, addressing turbidity, heavy metals, dissolved solids, and bacterial contamination simultaneously.